public with sharing class FeedbackController {
        
    public String retUrl{get;set;}
       
    public FeedbackController() {
         retUrl          = ApexPages.currentPage().getParameters().get('returl');         
         string txt      = ApexPages.currentPage().getParameters().get('txt');         
         
         if(null != retUrl)  retUrl = EncodingUtil.urlDecode(retUrl  , 'UTF-8');
         
         ApexPages.addmessage(new ApexPages.message(ApexPages.severity.ERROR, txt));
    }
    
}